The present application generally relates to motion control systems, and particularly to preventing windup in motion control systems, and more particularly to those used in systems like electric power steering (EPS) systems where closed-loop compensators are used for motion control of electric drive systems.
Typically, motion control systems employ electric actuators, which are control systems utilizing electrical machines and complementary power electronic modules controlled via digital signal processors for determining the compensation logic and driving the hardware circuitry. The hardware in such control systems have physical limitations, which is considered in the control system design in order to obtain optimal performance.
Motion control systems utilizing electrical actuators are implemented typically through a dual cascaded control structure, with the inner loop for controlling the currents and an outer loop for controlling the electromagnetic torque. The torque command is used to compute current commands considering multiple constraints depending on the machine and application under consideration.
Various motion control systems use a tracking compensator such as an integrator for accurate closed loop tracking. Examples of such systems include servomechanism for maintaining machine speed, closed loop handwheel torque in Electric Power Steering (EPS) systems, and handwheel position regulation schemes in Advanced Driver Assistance Systems (ADAS). Due to the limitations on the torque command and the actual torque, the control signal (torque) requested by the integrator may not be applied to the system. This discrepancy results in controller windup which degrades system performance and can lead to instabilities.